The instant Google Maps appeared, a lot of us knew right away that we’d never use MapQuest again. Google’s mapping and direction-finding service is a stunning improvement.

The maps are gorgeously readable, and they fill as much of the screen (or the printed page) as you give them. Scrolling the map works in the most natural way, by dragging the image. The mapping service dovetails with local.google.com, which finds businesses by city or ZIP code. In direction-finding mode, each step along the route offers a link that, when clicked, pops up an enlarged view of the intersection.

As is the tradition when Google launches a new service, curious hackers immediately took Google Maps apart to see how the magic was done. The best early analysis came from Joel Webber, who worked out the details of image tiling, dynamic updating, and route plotting (infoworld.com/2533). Among other interesting discoveries, he found that the application uses the browser’s built-in XSLT engine to transform packets of XML received from the server into search results, displayed as HTML.

Commenting on Webber’s post, one reader noted that no W3C standard defines this capability. As is the related XMLHttpRequest object, which enables the browser to programmatically fetch XML from the server and parse it, the built-in XSLT processor was a Microsoft innovation that was later copied by Mozilla. Safari and Opera do support XMLHttpRequest, by the way, which is why they can run Google Suggest, the experimental version of Google’s search that dynamically expands partially typed queries into lists of choices.

The W3C can bless this approach or not, but with Google Suggest and now Google Maps, Google has thrown down the gauntlet. The modern browser is an XML-aware client. Savvy Web developers have known about these features for a while, but now Google has legitimized them and pushed them squarely into the mainstream. My guess is that we’ll see an explosion of pent-up creativity as more Web developers discover, and begin to exploit, the full power available to them.

But wait, there’s more. If you append the term “output=xml” to any Google Maps URL, the server will send back an XML packet. APIs? We don’t need no stinking APIs. In 20 minutes I was able to build a proof-of-concept app -- made from snippets of HTML, JavaScript, and XSLT -- that accepts city names or ZIP codes and displays information about local businesses. (Unfortunately, the XML feature has since been disabled.)

I didn’t need to publish any new services to do that. Because the app uses the W3C’s hosted XSLT transformer in tandem with Google Maps, I was able to “deploy” it in any browser simply by posting an HTML/JavaScript snippet to my Weblog.

Google Maps’ killer integration hook is the latitude/longitude data woven into its queries and responses, which can tie into any geo-aware app. We don’t yet know how Google plans to control or monetize this capability, but it shows what can happen when all the pieces of Web technology come together in the right way.